## 实验3 选择结构程序设计 ### 实验任务 3-1.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210408-1617867164963) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210408-1617867206809) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210408-1617867963130) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210408-1617868018387) 3-3.c 运行结果截图：有折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210408-1617869275205) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210408-1617869296556) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210408-1617870061870) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210408-1617870076926) ### 上机练习 1、输入一个整数，输出它的绝对值。 - 方法1的代码 ```c #include #include int main() { int a,b,c,n; printf("please enter two number "); scanf("%d%d",&a,&b); n = fabs(a); c = sqrt(b*b); printf("%d ",n); printf("%d ",c); ``` - 运行结果截图：--![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210408-1617870866678) - - 方法2的代码 ```c #将修改后代码填在此处，然后删除这行文字 ``` - 运行结果截图： 2、输入一个字符，判断该字符是否是数字，若为数字，输出1，否则输出0。 - 代码 ```c #include int main() { char c; printf("please enter a character "); scanf("%c",&c); if (c>='0' && c<='9') printf("1"); else printf("0"); } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210410-1618022318665)d![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210410-1618022337801) 3、 [课后题3]，至少用两种方法实现，对比思考哪一种方法更好一些？ - 多分支方法实现的代码 ```c #include int main() { float x; printf("please enter a number"); scanf("%f",&x); if (x<0) printf("y = 0"); else if (x>=0 && x<10) printf("y = %f",x); else if(x>=10 && x<20) printf("y = %f",x+1); else if(x>=20 && x<30) printf("y = %f",2*x-1); else printf("y = %f",3*x+1); } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210410-1618059927940) - if嵌套方法实现的代码 ```c #include int main() { float x; printf("please enter a number "); scanf("%f",&x); if (x>30) printf("y = %f",3*x+1); else if(x>=20) printf("y = %f",2*x+1); else if(x>=10) printf("y = %f",x+1); else if(x>=0) printf("y = %f",x); else if(x<0) printf("y = 0"); } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210410-1618062350309) - 哪一种方法更好：第2种 4、 [课后题3]，至少用两种方法实现，对比思考哪一种方法更好一些？ - 任务一：练习PPT中最后一页里的菜谱题目，利用数字1-7表示的代码 ```c #include int main() { int date; printf("please enter a date(1-7) "); scanf("%d",&date); switch (date) { case 1:printf("Monday:qingcai");break; case 2:printf("Tuesday:ji");break; case 3:printf("Wednesday:yu");break; case 4:printf("Thursday:rou");break; case 5:printf("Friday:jidan");break; case 6:printf("Saturday:douzhipin");break; case 7:printf("Weekday:haixian");break; default:printf("error"); } } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210410-1618064009974) - 任务二：[课后题4]输入星期首字母，判断星期几，当遇到S或T时，需要再输入一个字母，从而判断出准确日期的代码 ```c #include int main() { char letter1,letter2,letter3; printf("please enter a letter\n"); scanf("%c",&letter1); switch(letter1) { case 'M':printf("Monday\n");break; case 'T': { printf("please enter a letter\n"); scanf("%c%c",&letter1,&letter2); switch(letter2) { case 'u':printf("Tuesday\n");break; case 'h':printf("Thursday\n");break; } } case 'W': { printf("please enter a letter\n"); scanf("%c%c%c",&letter1,&letter2,&letter3); switch(letter3) { case 'd':printf("Wendesday\n");break; case 'e':printf("Weekday\n");break; } } case 'F':printf("Friday\n");break; case 'S':printf("Saturday\n");break; } } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1526810-20210410-1618070288586)

“程序设计基础II”实验报告